The invention relates to a vehicle wheel suspension of a control blade design having three wheel-guiding control arms essentially oriented in the transverse direction of the vehicle, as well as having one longitudinal control arm fastened essentially rigidly to the wheel carrier and barely limiting its transverse movement with respect to the vehicle body. Concerning the state of the art, in addition to EP 0 136 563 B1 or DE 102011 112 053 A1, reference is made to DE 199 33 432 B4. While the last-mentioned document shows a special wheel suspension having a control arm made of a composite fiber material and designed as a leaf spring suspension, the two first-mentioned documents show vehicle wheel suspensions of the control blade design.
In the further development of rear axles, particularly for passenger cars, it is increasingly necessary to reduce installation space and weight while making the driving dynamics as good as possible. Furthermore, it is advantageous to have additional flexibility present for the arrangement of the individual axle components, so that, for example, different designs of the rear part of a vehicle class can be presented or different chassis control systems can optionally be integrated in a simple manner. It is an object of the present invention to provide an improvement in this respect for a control blade axle known to the person skilled in the art.
This and other objects are achieved by a vehicle wheel suspension of the control blade design having three wheel-guiding control arms essentially oriented in the transverse direction of the vehicle, as well as having one longitudinal control arm fastened essentially rigidly to the wheel carrier and barely limiting its transverse movement with respect to the vehicle body. The longitudinal control arm is essentially rigidly fastened to the vehicle body and thereby also takes over the function of the main spring between the wheel carrier and the vehicle body.
First, the term “essentially rigid fastening” will be briefly discussed, which is provided for the above-mentioned longitudinal control arm at the wheel carrier and at the vehicle body. This term has the purpose of expressing that, with respect to the element carrying it, i.e. with respect to the wheel carrier and with respect to the vehicle body, the control arm has no degree of freedom in the actual sense in the respective fastening point, so that this is not a joint of a somewhat different type but virtually a rigid connection. However, particularly for increasing the rolling comfort and/or for improving the acoustics in the vehicle, it may be recommended to fasten the longitudinal control arm slightly elastically to the vehicle body and/or to the wheel carrier. A defined degree of freedom will also not exist then and the above-mentioned elastic bearing takes over particularly a damping function mechanically with respect to brief hard shocks and/or acoustically with respect to otherwise transmitted rolling noises. By means of such a slightly elastic fastening, the longitudinal control arm is then “essentially rigidly” fastened to the wheel carrier and/or to the vehicle body.
With respect to the invention, it is known that good driving dynamics are represented by way of a so-called control blade axle with three wheel-guiding control arms oriented essentially in the transverse vehicle direction and a control arm oriented essentially in the longitudinal direction of the vehicle, which control arm is fastened to the wheel carrier and whose freedom of movement in the transverse direction of the vehicle is not significantly limited, at least to the extent that the latter can move because the transverse control arms continue to guide the wheel carrier.
Various arrangements are known for a main spring still required in addition to the wheel-guiding control arms, by which the vehicle body is proportionately supported at the wheel carrier. Thus, in European Patent Document EP 0 136 563 B1 first mentioned above, the main spring is supported directly at the wheel carrier, while, in the case of the initially further mentioned German Patent Document DE 102011 112 053 A1, the main spring (not shown there) is most probably supported on a rearward lower transverse control arm. The latter therefore has to have a relatively massive construction, which requires a relatively large amount of space and also significantly increases the weight of the vehicle. Furthermore, particularly in the case of driven axles, there is a limitation with respect to the possible arrangement of that transverse control arm that carries the main spring in order to achieve sufficient distance between the main spring and the drive shaft of the wheel. If, in contrast, according to an alternative design, the main spring is supported directly on the wheel carrier, the above-mentioned disadvantages do not exist, but the main spring would project very far upward viewed in the vertical direction, which is disadvantageous in the case of rear axles, particularly of passenger cars, for constituting a rear part of a vehicle with a large trunk, a large loading width and a favorable support structure.
In the present case, it is therefore suggested to integrate the main spring function in the longitudinal control arm of a so-called sword arm axle, which, in the state of the art, normally viewed in the transverse direction of the vehicle, has a relatively flexible construction. This longitudinal control arm, which in the state of the art is flexible in the transverse direction of the vehicle, with its end facing away from the wheel carrier is, swivelably about the transverse axis of the vehicle, fastened directly or indirectly to the vehicle body, in order to permit a compression and rebound travel of the wheel, i.e. its vertical movement. According to the present invention, this longitudinal control arm is now essentially rigidly fastened not only to the wheel carrier, but also to the vehicle body (except for a possibly slight elastic bearing), and, when viewed in the transverse direction of the vehicle, under a corresponding force effect, itself can be significantly elastically deformed such that the wheel can be displaced in the vertical direction by way of its usual spring travel or wheel travel. By way of this elastic deformation, which can be constituted under the effect of force, this longitudinal control arm can therefore at least proportionately take over the function of the main spring.
While the functional integration of one of the supporting springs in the longitudinal control arm according to the invention can, in principle, be constituted by use of different materials and further developments of the longitudinal control arm as well as manufacturing processes for this longitudinal control arm, additional weight-related advantages are obtained according to the invention, if this above-mentioned deformability of the longitudinal control arm, while the shaping is suitable, is generated in that this longitudinal control arm is constructed of a composite fiber material. When the shaping is suitable, by means of such an implementation, advantageously, the required elasticity in the transverse direction of the vehicle can also be more easily constituted.
A longitudinal control arm according to the invention in a vehicle rear axle of the control blade design therefore significantly limits the mobility of the wheel carrier only in the longitudinal direction of the vehicle, whereas its mobility in the transverse direction of the vehicle is barely limited by a longitudinal control arm according to the invention and its mobility in the vertical direction is limited only to an extent that this longitudinal control arm at least proportionately takes over the function of a main spring clamped in between the wheel carrier and the vehicle body. Therefore, in addition to the longitudinal control arm according to the invention, an additional spring element may also be clamped in at a vehicle wheel suspension according to the invention between the vehicle body and (finally) the wheel carrier, which then, however, can have significantly smaller dimensions than in the case of the conventional state of the art (of a control blade design axle). A longitudinal control arm according to the invention will, however, preferably completely take over the function of an otherwise customary main spring, so that, according to the state of the art, only a compression stop spring and/or rebound stop spring is still provided, which is integrated in a vibration damper functionally connected parallel to the main spring. This compression stop spring and/or rebound stop spring acts or can act between the wheel carrier and the vehicle body.
In order to realize different spring rates of the main spring as well as for the adaptation to different vehicle weights in the design position, it may be helpful that the longitudinal control arm according to the invention is constructed with several control arm branches, particularly when the geometrical and material-related scope of design options is not sufficient using a single control arm or control arm branch, for meeting the required application range of the axle. The above-mentioned longitudinal control arm can therefore be formed by two or more, in a wide area, individual control arm parts, which are preferably situated essentially in a common vertical plane, whereby, on the one hand, a considerable degree of freedom exists with respect to the geometrical design of this longitudinal control arm and therefore also its suspension characteristics and other features. On the other hand, particularly when the first control arm part of the longitudinal control arm is situated above and the second control part is situated below the wheel center at the wheel carrier, a wheel drive shaft can extend between these two control arm parts through to the hub of the wheel carrier. When these two (or more) control arm parts, guided together with their other ends, are fastened in a common fastening element to the vehicle body, this reduces the building expenditures and simplifies the mounting process for a wheel suspension according to the invention.
In order to optimize the rolling comfort and the rolling acoustics with respect to the longitudinal control arm according to the invention, it may be helpful for the vehicle-body-side end of the longitudinal control arm to be elastically disposed or fastened, for example, in rubber. By means of such a slightly elastic fastening or bearing, it is further contemplated to shape the introduction of force onto the longitudinal control arm to be flat, whereby undesirable point loads or line loads are avoided. For this purpose, rounding-off of a fastening element for the longitudinal control arm can be used in the area of an opening of this element, into which the longitudinal control arm is inserted. Furthermore, an elastic fastening can seal off the body-side fixation point and the entering of water, dirt and particles can thereby be prevented. Such a slightly elastic fastening can be constituted particularly easily when the body-side end of the longitudinal control arm is vulcanized into the fastening element to be rigidly connected with the vehicle body. If the introduction area of the fastening element for the longitudinal control arm is in this case provided with diagonal walls, which taper toward the entrance opening for the longitudinal control arm, it is easily ensured that even in the case of a high longitudinal force load against the traveling direction toward the rear, as it may occur, for example, when braking or driving over a pothole, the longitudinal control arm and the fastening element will not separate from one another. In order to meet the highest demands with respect to rolling comfort and acoustics or, if required, eliminate operational stability problems at the wheel-carrier-side fastening of the longitudinal control arm, such a slightly elastic fastening of the longitudinal control arm can also be provided at the wheel carrier.
In the case of a vehicle wheel suspension of the control blade type according to the invention, a braking torque resulting from a braking operation during forward driving is superimposed at the body-side fixation point of the longitudinal control arm in the same direction on the clamping-in torque from the wheel load, which may result here in a compensation of the rebounding movement at the rear axle usually caused by the braking. In this case, a rebounding movement can be compensated partially, completely or even be overcompensated as a function of the geometrical conditions. In comparison to a classically implemented sword arm axle, as illustrated, for example, in EP 0 136 563 B1, this means that, in the case of a wheel suspension according to the invention, the body-side fixation point of the longitudinal control arm can be selected to be lower, without having to fear disadvantages in the anti-dive behavior of the vehicle. This results in additional installation space advantages, which permit an advantageous and therefore weight-optimized structural design of the vehicle body.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.